GB1587523A - Multi-circuit protective valve assemblies for compressed air systems - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO MULTI-CIRCUIT PROTECTIVE VALVE ASSEMBLIES FOR COMPRESSED AIR SYSTEMS (71) We, ROBERT BOSCH GmbH, a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particu larly described in and by the following statement: The present invention relates to multi circuit protective valves for compressed air systems.

It is customary to provide a multi-circuit protective valve assembly in multi-circuit compressed air systems to protect each circuit in such a manner that, if one circuit fails, the other circuits may still be supplied and are protected from being out of action. Such a multi-circuit protective valve assembly has for each circuit to be protected a valve seat which is closable by a closure member subject to an adjustable spring force, and a throttle is disposed upstream of the valve thus formed.

In one known multi-circuit protective valve a throttle point is formed at a second circum ferential joint disposed concentrically to a first circumferential joint in that this second circumferential joint is provided with a radial opening (German Offenlegungsschrift 2 355 456).

A disadvantage of this known construction is that because of the second circumferential joint additional forces become active on the valve which have a negative effect when the valve is closed.

Because of variation of adjustment when adjusting the spring loading of each closure member it is practically impossible to adjust the valves of a multi-circuit protective valve assembly identically. This means that the valves may have varying opening pressures. A pressure difference of approximately 0.3 bar is considered a normal adjusting variation. With such adjustment variations, a lower set circuit receives air first and then the higher set circuit. If a defect then occurs in the lower set circuit in such a manner that this circuit is relieved of pressure, it must still be ensured that the intact higher set circuit can receive air.

In known multi-circuit protective valve assemblies, to meet this requirement a permanent throttle is disposed upstream of each of the valves in order to provide an additional pressure head in the supply line. This higher pressure head is sufficient to open the valve which is set higher within the range of variation adjustment.

When it comes to filling an empty but intact circuit this arrangement has the disadvantage that the small through-flow cross-section of the permanent throttle, especially when a large quantity of air is to be supplied, may give rise to a pressure in the supply line which is above the cut-off valve of a pressure regulator. The cut-off occurring before all the circuits are filled. If the throttle action of the throttles is reduced to lessen this disadvantage, the variation of adjustment of the valves has to be restricted in order to enable a defective circuit to be filled since the pressure head which arises is not so great.

This reduction of variations of adjusting does however, as already described, present great difficulties.

According to the present invention there is provided a multi-circuit protective valve assembly for compressed air systems for motor vehicles, said multi-circuit protective valve assembly being adapted to be disposed between an air compressor and several air reservoirs and having for each compressed air supply circuit to a respective reservoir a valve whose closure member is urged by an adjustable pressure setting spring against an annular valve seat surrounding a shallow recess and a respective coaxial compressed air inlet passage such that when the closure member is first lifted from the valve seat by the inlet supply pressure a throttle is formed by the annular gap between the closure member and the base of the shallow recess to throttle the compressed air flowing from the respective inlet and through the opened valve to the respective compressed air supply circuit.

An advantage of a multi-circuit protective valve embodying the present invention is that a variable throttle gap is produced which varies in response to the pressure head and the quantity of air supplied; i.e. with a smaller throughflow quantity there is a narrower throttle gap since the pressure head below the closure mem ber is lower, and with a larger throughflow quantity and therefore a greater pressure head the throttle gap increases. Thus, it is possible on the one hand to fill a defective circuit in the event of a low supply quantity and maximum variation of adjustment and on the other hand premature switching of the pressure regulator with a large supply quantity is avoided. During the closing process of a valve, no additional disruptive forces arise between the valve seat and the closure member.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatical section through a valve for a multi-circuit protective valve assembly, and Figure 2 is a section through a multi-circuit protective valve assembly.

Figure 1 shows a section through an operating unit for a circuit of a multi-circuit protective valve for one circuit from which others are to be protected. It should be noted that in practice several such units may be combined one after another in series or in parallel, either in pairs or in groups one behind another - possibly with non-return valves placed there between to form a multi-circuit protective valve.

The operating unit has a cylindrical housing 1 provided with a multi-stepped bore 2. A valve seat 4 is formed on one bore shoulder 3 on which a flat recess 5 is provided.

An inlet passage 6 communicates centrally in to this recess 5 so that of the recess 5 only an annular surface 7 remains.

Resting on the valve seat 4 is a radial sealing surface 8' of a plastics valve closure member 8 whose side remote from the valve seat 4 is provided with a metal reinforcement 9. The closure member 8 and the metal reinforcement 9 have an axially directed extension 10 and 11 and the closure member extension 10 is provided at its end with an annular sealing lip 12.

This annular sealing lip 12 lies against outer wall 13 of a guide cylinder 14 which, sealed off by means of a flange 15 moulded thereon, is inserted in the bore 2 and is held in said bore against a shoulder 16 by a disc 17 and a circlip 18.

A spring 19 is disposed in the cylinder 14 with one end of the spring engaging the closure member 8. The other end of spring engages a valve spring retainer 20 located on the head of a screw 21 which is adjustable in the disc 17. A chamber 22 lies between the inner wall of the bore 2 and the outer wall 13 of the cylinder 14.

It is obvious that the flat recess 5 may be provided in the closure member 8 instead of in the valve seat 4. Each operating unit constitutes a protective valve.

Figure 2 shows a section through a housing 31 having as protective valves, two operating units 23 and 24 as illustrated in Figure 1.

Two passages 26 and 27 which lead to the inlet passage 6 of each operating unit 23 and 24 are connected to a central bore 25. When in use the bore 25 is supplied with compressedair from a compressor (not shown). The two chambers 22 are connected by connections 28,28' to air reservoirs (not shown) associated one with each circuit I and II.

Let it now be assumed that within the range of the variations in adjustment the circuit II is set higher than the circuit I. When the opening pressure for circuit I is reached, air flows into the air supply reservoir of this circuit. The annular gap 7 provided through the recess 5 operates as a preconnected inlet throttle and, with the air quantity supplied corresponding at least to the supply quantity of the smallest conventional compressor during idling of the vehicle motor, has the effect of increasing the pressure in the inlet passages 6. Opening of the valve for circuit 11 is then possible when, by suitably selecting the throttle annular gap 7, the pressure head in the inlet passage 6 rises above the adjusted opening pressure for circuit 11.

A throttle constructed in this manner decreases in efficiency as the supply quantity from the compressor, and therefore the pressure head upstream of the operating unit 23 or 24, increases. The throttle becomes ineffective as soon as the valve closure member 8 is additionally acted upon by the pressure in the chamber 22 and detaches itself from its valve seat 4 against the force of the spring 19.

WHAT WE CLAIM IS : 1. A multi-circuit protective valve assembly for compressed air systems for motor vehicles, said multi-circuit protective valve assembly being adapted to be disposed between an air compressor and several air reservoirs and having for each compressed air supply circuit to a respective reservoir a valve whose closure member is urged by an adjustable pressure setting spring against an annular valve seat surrounding a shallow recess and a respective coaxial compressed air inlet passage, such that when the closure member is first lifted from the valve seat by the inlet supply pressure a throttle is formed by the annular gap between the closure member and the base of the shallow recess to throttle the compressed air flowing from the respective inlet and through the opened valve to the respective compressed air supply circuit.

2. A multi-circuit protective valve as claimed in Claim 1, in which the shallow recess is located radially inside the valve seat.

3. A multi-circuit protective valve as claimed in Claim 1, in which the shallow recess is disposed in the closure member radially inwardly of the valve seat.

4. A multi-circuit protective valve as claimed in Claim 1, 2 or 3, in which the recess is annular.

5. A multi-circuit protective valve assembly constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. ber is lower, and with a larger throughflow quantity and therefore a greater pressure head the throttle gap increases. Thus, it is possible on the one hand to fill a defective circuit in the event of a low supply quantity and maximum variation of adjustment and on the other hand premature switching of the pressure regulator with a large supply quantity is avoided. During the closing process of a valve, no additional disruptive forces arise between the valve seat and the closure member. The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatical section through a valve for a multi-circuit protective valve assembly, and Figure 2 is a section through a multi-circuit protective valve assembly. Figure 1 shows a section through an operating unit for a circuit of a multi-circuit protective valve for one circuit from which others are to be protected. It should be noted that in practice several such units may be combined one after another in series or in parallel, either in pairs or in groups one behind another - possibly with non-return valves placed there between to form a multi-circuit protective valve. The operating unit has a cylindrical housing 1 provided with a multi-stepped bore 2. A valve seat 4 is formed on one bore shoulder 3 on which a flat recess 5 is provided. An inlet passage 6 communicates centrally in to this recess 5 so that of the recess 5 only an annular surface 7 remains. Resting on the valve seat 4 is a radial sealing surface 8' of a plastics valve closure member 8 whose side remote from the valve seat 4 is provided with a metal reinforcement 9. The closure member 8 and the metal reinforcement 9 have an axially directed extension 10 and 11 and the closure member extension 10 is provided at its end with an annular sealing lip 12. This annular sealing lip 12 lies against outer wall 13 of a guide cylinder 14 which, sealed off by means of a flange 15 moulded thereon, is inserted in the bore 2 and is held in said bore against a shoulder 16 by a disc 17 and a circlip 18. A spring 19 is disposed in the cylinder 14 with one end of the spring engaging the closure member 8. The other end of spring engages a valve spring retainer 20 located on the head of a screw 21 which is adjustable in the disc 17. A chamber 22 lies between the inner wall of the bore 2 and the outer wall 13 of the cylinder 14. It is obvious that the flat recess 5 may be provided in the closure member 8 instead of in the valve seat 4. Each operating unit constitutes a protective valve. Figure 2 shows a section through a housing 31 having as protective valves, two operating units 23 and 24 as illustrated in Figure 1. Two passages 26 and 27 which lead to the inlet passage 6 of each operating unit 23 and 24 are connected to a central bore 25. When in use the bore 25 is supplied with compressedair from a compressor (not shown). The two chambers 22 are connected by connections 28,28' to air reservoirs (not shown) associated one with each circuit I and II. Let it now be assumed that within the range of the variations in adjustment the circuit II is set higher than the circuit I. When the opening pressure for circuit I is reached, air flows into the air supply reservoir of this circuit. The annular gap 7 provided through the recess 5 operates as a preconnected inlet throttle and, with the air quantity supplied corresponding at least to the supply quantity of the smallest conventional compressor during idling of the vehicle motor, has the effect of increasing the pressure in the inlet passages 6. Opening of the valve for circuit 11 is then possible when, by suitably selecting the throttle annular gap 7, the pressure head in the inlet passage 6 rises above the adjusted opening pressure for circuit 11. A throttle constructed in this manner decreases in efficiency as the supply quantity from the compressor, and therefore the pressure head upstream of the operating unit 23 or 24, increases. The throttle becomes ineffective as soon as the valve closure member 8 is additionally acted upon by the pressure in the chamber 22 and detaches itself from its valve seat 4 against the force of the spring 19. WHAT WE CLAIM IS :

1. A multi-circuit protective valve assembly for compressed air systems for motor vehicles, said multi-circuit protective valve assembly being adapted to be disposed between an air compressor and several air reservoirs and having for each compressed air supply circuit to a respective reservoir a valve whose closure member is urged by an adjustable pressure setting spring against an annular valve seat surrounding a shallow recess and a respective coaxial compressed air inlet passage, such that when the closure member is first lifted from the valve seat by the inlet supply pressure a throttle is formed by the annular gap between the closure member and the base of the shallow recess to throttle the compressed air flowing from the respective inlet and through the opened valve to the respective compressed air supply circuit.

2. A multi-circuit protective valve as claimed in Claim 1, in which the shallow recess is located radially inside the valve seat.

3. A multi-circuit protective valve as claimed in Claim 1, in which the shallow recess is disposed in the closure member radially inwardly of the valve seat.

4. A multi-circuit protective valve as claimed in Claim 1, 2 or 3, in which the recess is annular.

5. A multi-circuit protective valve assembly constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.